1. Field of the Invention
The present invention relates generally to building ventilation systems, and more particularly to a system capable of operating to exhaust harmful smoke away from occupants of a building when a dangerous smoke level is detected.
2. Description of the Known Art
All too often we hear of persons having perished on account of building fires, not because they did not have enough time to evacuate the building from the time when flames first erupted until the building was consumed by the fire, but because they became disabled by smoke inhalation.
Many kinds of fires erupting inside today's buildings will generate extremely hazardous levels of smoke on account of their origin (e.g., chemicals, synthetic material and the like) and/or because insufficient ventilation is available to exhaust the smoke as it evolves. The latter situation is compounded by construction practices in modern buildings in which windows are permanently sealed and, thus, cannot be readily used by occupants as a means for venting smoke unless physically broken open with a heavy, hard object. It will be appreciated that during a time of panic, the smashing open of building windows by the occupants so that they will not become engulfed with smoke, is not a practice that should be taught or encouraged. Particularly at floor levels high above the street, the breaking open of modern floor-to-wall window panels would only further endanger the building occupants as well as persons below at the street level.
Most local ordinances today mandate that public buildings contain some form of smoke and/or fire detection apparatus, and suitable alarm mechanisms to alert occupants to a fire or smoke condition. Stairways or other means of egress from the building are provided for the occupants to use in such an emergency. Unfortunately, most occupants do not familiarize themselves with the location of fire exits provided in buildings so that when an alarm is sounded, they must take time to learn the whereabouts of the appropriate doors and stairways. Even for those occupants with prior knowledge of the emergency exits, the sudden eruption of a dense smoke producing fire will tend to blind them and cause panic. If an occupant cannot see his or her way clear to a fire exit even when crawling at floor level, the chances of safely exiting the building prior to succumbing to smoke inhalation are drastically reduced.
As far as is known, no system exists by which a potentially dangerous level of smoke quickly evolving inside a building, can be positively and rapidly exhausted away from the building occupants at least to give them sufficient time to evacuate the building safely. Most buildings today include air conditioning systems in which conditioned air is supplied through a supply duct system under a slightly positive pressure with the aid of a supply motor. The supply duct system thus is arranged to force air into, rather than evacuate a room with which the duct system communicates through a register. Further, local ordinances require the provision of fire dampers at certain locations along the length and inside building duct systems to prevent propagation of a fire through the ducting when the dampers close. A fuseable link associated with each damper melts at a certain elevated temperature indicative of a fire in the vicinity of the damper, thus causing the damper to move from an open to a closed position and block the ducting passage.